Patch for bug 74983 (among others) to be applied to M11 696 branch.

content/common/file_path_watcher/file_path_watcher.h

+// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// This module provides a way to monitor a file or directory for changes.
+
+#ifndef CONTENT_COMMON_FILE_PATH_WATCHER_FILE_PATH_WATCHER_H_
+#define CONTENT_COMMON_FILE_PATH_WATCHER_FILE_PATH_WATCHER_H_
+#pragma once
+
+#include "base/basictypes.h"
+#include "base/file_path.h"
+#include "base/message_loop_proxy.h"
+#include "base/ref_counted.h"
+
+// This class lets you register interest in changes on a FilePath.
+// The delegate will get called whenever the file or directory referenced by the
+// FilePath is changed, including created or deleted. Due to limitations in the
+// underlying OS APIs, FilePathWatcher has slightly different semantics on OS X
+// than on Windows or Linux. FilePathWatcher on Linux and Windows will detect
+// modifications to files in a watched directory. FilePathWatcher on Mac will
+// detect the creation and deletion of files in a watched directory, but will
+// not detect modifications to those files. See file_path_watcher_mac.cc for
+// details.
+class FilePathWatcher {
+ public:
+  // Declares the callback client code implements to receive notifications. Note
+  // that implementations of this interface should not keep a reference to the
+  // corresponding FileWatcher object to prevent a reference cycle.
+  class Delegate : public base::RefCountedThreadSafe<Delegate> {
+   public:
+    virtual ~Delegate() {}
+    virtual void OnFilePathChanged(const FilePath& path) = 0;
+    // Called when platform specific code detected an error. The watcher will
+    // not call OnFilePathChanged for future changes.
+    virtual void OnFilePathError(const FilePath& path) {}
+  };
+
+  FilePathWatcher();
+  ~FilePathWatcher();
+
+  // Register interest in any changes on |path|. OnPathChanged will be called
+  // back for each change. Returns true on success.
+  // OnFilePathChanged() will be called on the same thread as Watch() is called,
+  // which should have a MessageLoop of TYPE_IO.
+  bool Watch(const FilePath& path, Delegate* delegate) WARN_UNUSED_RESULT;
+
+  class PlatformDelegate;
+
+  // A custom Task that always cleans up the PlatformDelegate, either when
+  // executed or when deleted without having been executed at all, as can
+  // happen during shutdown.
+  class CancelTask : public Task {
+   public:
+    CancelTask(PlatformDelegate* delegate): delegate_(delegate) {}
+    virtual ~CancelTask() {
+      delegate_->CancelOnMessageLoopThread();
+    }
+
+    virtual void Run() {
+      delegate_->CancelOnMessageLoopThread();
+    }
+   private:
+    scoped_refptr<PlatformDelegate> delegate_;
+
+    DISALLOW_COPY_AND_ASSIGN(CancelTask);
+  };
+
+  // Used internally to encapsulate different members on different platforms.
+  class PlatformDelegate : public base::RefCountedThreadSafe<PlatformDelegate> {
+   public:
+    PlatformDelegate();
+
+    // Start watching for the given |path| and notify |delegate| about changes.
+    virtual bool Watch(const FilePath& path,
+                       Delegate* delegate) WARN_UNUSED_RESULT = 0;
+
+    // Stop watching. This is called from FilePathWatcher's dtor in order to
+    // allow to shut down properly while the object is still alive.
+    // It can be called from any thread.
+    virtual void Cancel() = 0;
+
+   protected:
+    virtual ~PlatformDelegate();
+
+    // Stop watching. This is only called on the thread of the appropriate
+    // message loop. Since it can also be called more than once, it should
+    // check |is_cancelled()| to avoid duplicate work.
+    virtual void CancelOnMessageLoopThread() = 0;
+
+    scoped_refptr<base::MessageLoopProxy> message_loop() const {
+      return message_loop_;
+    }
+
+    void set_message_loop(base::MessageLoopProxy* loop) {
+      message_loop_ = loop;
+    }
+
+    // Must be called before the PlatformDelegate is deleted.
+    void set_cancelled() {
+      cancelled_ = true;
+    }
+
+    bool is_cancelled() const {
+      return cancelled_;
+    }
+
+   private:
+    friend class base::RefCountedThreadSafe<PlatformDelegate>;
+    friend class CancelTask;
+
+    scoped_refptr<base::MessageLoopProxy> message_loop_;
+    bool cancelled_;
+  };
+
+ private:
+  scoped_refptr<PlatformDelegate> impl_;
+
+  DISALLOW_COPY_AND_ASSIGN(FilePathWatcher);
+};
+
+#endif  // CONTENT_COMMON_FILE_PATH_WATCHER_FILE_PATH_WATCHER_H_